The use of a sweeping jet fluidic oscillators for defrosting/defogging operation for automobile windshields is disclosed in the following patents issued to the assignee hereof: 4,250,799, 4,336,909, 4,365,540, 4,428,277, 4,437,392, 4,517,881, 4,644,854, 4,672,886, 4,686,890, 4,694,992, 4,709,622, 4,823,682, 4,941,398.
All the above patents are assigned to the assignee of the present application.
In Kakei et al. U.S. Pat. Nos. 3,745,906 and 3,832,939, several forms of sweeping jet oscillators for defrost purposes are disclosed, one of which included a fluidic oscillator in which a pair of cross feedback pipes receive portions of air issuing from the outlet downstream of the throat and return same to a pair of control ports. In some of the Stouffer patents mentioned above, a vibrating reed oscillator is utilized which significantly reduce the amount of space under the dash. In some other prior art sweeping jet systems, including Kakei et al., electromagnets were used to control valves for the switching purposes and these require unnecessary complexities and require a fluidic logic element of at least 5W length in order to get adequate sweeping angles where W is the width of the power nozzle. Fluidic oscillators based on a continuous passage or loop interconnecting the pair of control ports of the fluidic element are known in the art and disclose further, for example, in Stouffer et al. Patent 4,644,854 mentioned above.
The present invention is an improvement in that it maximizes the thermal energy transfer to or from a windshield for defrost/defog purposes and, at the same time, reduce the manufacturing cost and complexities of the oscillating fluidic element and improves the form factor and eliminates extraneous elements and connections. According to the present invention, thermal energy transference to or removed from a glass plate is maximized by projecting an oscillating air jet through a predetermined distance from a nozzle aimed at the plate so that an oscillating jet impinges on a plate at a predetermined angle of impingement and the jet is caused to oscillate at a rate such that the wavelength of the projected air is greater than the predetermined distance from the nozzle to the plate and smaller than the length of the plate in the direction of the air jet propogation across it so that there is less loss or gain of thermal energy from the air jet in the short space between the nozzle and the plate and a maximum transfer of thermal energy to the plate within the predetermined length which is accomplished to lessening the thickness of any insulating boundary layer as the air is moved or propogated over the plate.
In a preferred embodiment, a fluidic oscillator in which the wavelength is a constant independent of changing pressure such as the type disclosed in my patent 4,151,955 (incorporated herein by reference)is utilized.